Comparison of the Energy Efficiency of Synchronous Power Generator with Spark Ignition Engine using Different Types of Fuels

Stefan Zaichenko[0000-0002-0704-4116], Denys Derevianko[0000-0002-4877-5601]

National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”, Kyiv, Ukraine

zstefv@gmail.com

Abstract. This chapter presents experimental studies to determine the energy performance of the generator using gasoline and liquefied petroleum gas. The following are selected as energy indicators using liquefied petroleum gas and gasoline: specific fuel consumption and energy efficiency factor of the power plant. The highest specific fuel consumption is observed at the lowest and heaviest loads. It has been found that the highest values of efficiency for different fuels are observed at different loads. The established values of the distribution of energy indicators allow to predict the optimal parameters of autonomous installations using different types of fuels at different load levels. An analytical model describing a test system for diagnosing an autonomous generator based on a single-cylinder four-stroke internal combustion engine makes it possible to determine energy efficiency. The mathematical model developed allows to determine the technical condition of the autonomous generator by the main parameter of the cylinder piston group of the internal combustion engine - the true compression ratio. The basis for determining an autonomous power generator condition is a test diagnosis system, which is based on the analysis of the starter motor generators current in different modes without fuel supply. As a new criterion for determining condition of an autonomous power generator based on the internal combustion engine, ratio of the average value of starter motor current when scrolling the depressed system and in the compressor, state is proposed. Setting a true compression ratio allows to determine the main parameters of the systems energy efficiency.

Keywords: electric generator, liquefied petroleum gas, gasoline, spark ignition engine, autonomous power source, technical condition, internal combustion engine, starting current

Efficiency of the synchronous electric generator with the engine with spark ignition operating on various types of gasoline fuel

World’s energy strategy supports the course of rational "minimization" of energy use. In particular, in Ukraine a significant increase in the share of renewable energy sources and off-balance energy resources is planned to reach 57.73 million toe at the level of 2030 compared to 15.51 million toe used in 2005 (an increase of 3.72 times). According to the forecasts, growth of electricity production by renewable energy sources power plants in Ukraine (excluding electricity production at small hydropower plants and biofuels in the baseline scenario) was expected to the level of 50 million kWh in 2010; 800 - in 2015; 1500 - in 2020; 2000 million kWh - in 2030. At the same time, electricity production by industrial and municipal power units was expected to increase to 9.85 billion kWh in 2010; 10.8 - in 2015; 11.4 – in 2020; 13.5 billion kWh in 2030 [1, 2]. Analysis of the dynamics and structure of Ukraine’s electricity production sector over the past two years (2019-2020) shows a steady increase in the share of autonomous power generation in total electricity production from 1 to 2%, respectively 2372 million kWh and 5 357 million kWh.

This feature is explained by the development of autonomous power supply systems, which not only complement stationary power plants, but in many cases provide solutions to important technical problems of power supply in distant areas. Autonomous energy units allow consumers to be independent from the centralized energy supply and to use the technologies, optimal for these conditions in accordance to the Smart Grid concept [3]. In different modes of the power supply system operation, electric generators usually operate with nominal load. This is due to the need for a reserve to provide electricity to variable amount of energy consumers.

Analysis of the autonomous energy sources market, shows a fairly narrow range of generators [4]. The most common variant of an autonomous energy source (more than 50% of all units) are gasoline generators with spark ignition with a synchronous electric generator of 2.5-3.5 kW rated capacity.

The actual efficiency of the generator unit in case of underload depends on the efficiency of the engine and the efficiency of the synchronous generator operating at different loads. There is a number of methods for determination of these parameters for both internal combustion engines (ISO 15550: 2016) and for synchronous generators (DSTU IEC 60034-2-1: 2019). However, the application of these methods for autonomous generators is complicated due to the need of examination of the individual components, the internal combustion engine and the generator, which in some cases is impossible to define due to their design. That is why consideration of the system states, as a whole is needed to facilitate the process of setting the parameters of engine- generator system performance.

To use the specified approach, it is necessary to modernize the existing methods of research of autonomous electrical units at different load levels, which are generally aimed at determining the power supply quality indicators in nominal operating modes or other to nominal (overload) conditions.

A number of works, which can be divided into two main groups, are devoted to the analysis of energy efficiency parameters of units based on internal combustion engines. The first group considers the process of determining the energy parameters by studying mainly the characteristics of the internal combustion engine. In this case, as a characteristic of energy efficiency the ratio of fuel consumption rate to engine’s capacity - brake-specific fuel consumption is used. This approach is based on the fact that the main losses of units fall on the internal combustion engine [5]. The second group of studies is devoted to the analyses of power unit as a whole, in some cases considering the energy performance of system’s components. Energy efficiency in this case is assessed by the ratio of generated power and fuel consumption. A characteristic which is common for these studies is the determination of energy efficiency indicators for units with load variation. Also in both research groups the internal combustion engine is connected to the electromechanical load - an electric brake or the generator.

Among the total scope of papers of the first group part of the papers are devoted to the use of mixtures of alternative fuels with mineral fuels. These studies mainly experimentally investigate the influence of various factors (the ratio of biofuels to mineral fuels, gas and liquid fuels, speed, angle of advance of the spray or ignition) on energy performance indicators of the units. The main purpose of aforementioned research papers is to confirm the possible reliable and safe for the environment use of alternative fuels. A number of studies note the independence of specific consumption from the power plant type [6].

In the paper [7] on operation optimization of the power unit which use a mixture of fuels (hydrogen and gasoline) the concentration of fuels and the speed of the shaft of generators with internal combustion engine are used as a main factors. The established pattern is the optimal efficiency value change at different concentrations of the fuel mixture and the load, which allows to optimize the generation process by using different mixtures. To determine the conditions that correspond to the optimal value of the efficiency ratio, most experiments were conducted on the minimum power values (<50%) of the 2.5 kW unit and do not cover the entire possible range of capacity.

The papers [8-10] aimed at studying the efficiency increase of a spark ignition engine with the conversion of the thermal energy of exhaust gases into electricity using a thermoelectric generator. When power increases from 25 to 75 kW, there is no significant change in specific fuel consumption (within 3%), which differs significantly from the known data.

The general characteristic of the presented works includes the rarity of the described fuel mixtures and methods of electricity generation. Quite small attention is paid to the: conditions of the experiment, the influence of engine parameters, rheological parameters of the fuel, namely the density of the fuel. Also, the studied models of autonomous generators and motors have a narrow use for power supply as backup sources.

Given above, it is possible to conclude that it is necessary to study the energy performance of a common generator type, namely a synchronous generator with a spark ignition engine. Also a special attention should be paid to the type and conditions of fuel use, which are maximally represented at the market.

The purpose of this study is to determine the energy performance indicators of the autonomous electric generators based on spark ignition engines using the most common fuels.

Energy performance indicators that are necessary for the modeling of the power supply systems dynamics and technical and economic indicators in the new power systems are as follows:

fuel consumption for electricity generation at different load levels, g / kWh;

efficiency at different load levels.

Two types of the most common used fuels for the conducted experiments:

-	automobile gasoline A-95 - Euro5;

-	automobile gasoline A-95 - Euro5 - E7.

The experiments were performed indoors at a temperature of (298 ± 3) K [(25 ± 3) °C] and relative humidity (95 ± 3) %. The value of atmospheric pressure was in the range of 755-165 mm Hg. Art. (100658-101991 Pa). Under these conditions, one of the main rheological parameters of the fuel, density, was determined. So, for A-95 - Euro5 it was – 735 kg/m3, and for A-95 - Euro5 - E7 – 757 kg/m3.

Among the wide range of autonomous generators, the authors paid attention to generating units based on a single- cylinder gasoline four-stroke internal combustion engine with an engine displacement of 200 cm3. Technical characteristics are given in Table 1. Most generators use as an alternator a synchronous generator with automatic voltage regulator (AVR), which contains the rotor and stator windings. The rotor speed of the generator is maintained by a centrifugal frequency regulator connected to the carburetor.

Table 1.	Technical characteristics of the synchronous electric generator with the spark ignition engine

Parameter	Unit	Value
Engine type	-	4-stroke gasoline engine with air cooling OHV
Number of cylinders	pcs	1
Engine model	-	H-168
Engine capacity	cm3	196
Engine power	W	4780
Maximum power of the generator	W	2800
Fuel tank volume	m3	0.015

Fig. 1 demonstrates a schematic representation of the experimental setup with measuring devices. The basis of the experimental unit is an autonomous electric synchronous generator - 1 with a spark ignition engine - 2. The carburetor of the engine 3 is disconnected from the tank (not shown) and connected to the vessel with the divisions marked on it 4. Synchronous generator - 1 is connected to the loader in the form of a liquid rheostat - 5. Power measurement is performed by registering the voltage on the generator panel and Hall’s current sensor - 6. Analog signal from the current sensor YHDC HK 16 and voltage sensor based on inductive module with voltage transformer series ZMPT101B is converted by 14-bit data acquisition microsystem -DAQ12 - 7 with fixing on the computer - 8.

The Brake Specific Fuel Consumption (BSFC) of the generation unit at different load levels for gasoline is equal to the ratio of fuel mass m to the amount of electricity generated, ΔP:

(1)

where – fuel density; – volume of fuel; – time; and - current and voltage of the stator of the generator.

The BSFC at different load levels for gasoline was calculated for a constant amount of gasoline 50ml.

Efficiency at different load levels is equal to the ratio of the amount of electricity generated to fuel combustion energy :

(2)

where – specific heat of combustion of fuel.

a b

Fig. 1. Experimental electric generator unit with a spark ignition engine using automobile gasoline: a) schematic representation; b) experimental unit itself

Tables 2 and 3 show the results of the experiment and calculated energy efficiency indicators according to the established data of voltage and current changes at different loads (N0=2500W).

Table 2.	Energy efficiency parameters of the electric generator for A-95 gasoline - Euro5

№	N/ N0	t, s	r, g/s	BSFS , g/J	BSFS, g/(kW·h)	
1	0	97	0.15608	-	-	-
2	0.2	89	0.17011	0.00033	1189.21	0.0688
3	0.4	70	0.21629	0.00021	756.00	0.1082
4	0.6	62	0.24419	0.00015	569.03	0.1437
5	0.8	44	0.34409	0.00016	601.36	0.1360
6	1	21	0.68818	0.00026	962.18	0.0850

Analyzing the data given in tables 1 and 2 it is necessary to determine the reduction of operating time of the generator Δt and, accordingly, an increase in fuel consumption r on average by 4.3%, due to the lower calorific value of alcohol-containing gasolines.

Table 3.	Energy efficiency parameters of the generator for gasoline A-95 - Euro5 - e7

№	N/ N0	m, g	r , g/s	BSFS , g / J	BSFS , g/(kW·h)	
1	0	27	0.09	-	-	-
2	0.2	35	0.117	0.00034	720.4	0.106
3	0.4	47	0.157	0.000133	480.2	0.160
4	0.6	55	0.183	0.000183	360.2	0.213
5	0.8	75	0.250	0.000125	342.1	0.224
6	1	96	0.320	0.000128	384.8	0.200

The analysis of the data from Tables 2 and 3 is presented graphically and represents the changes in specific fuel consumption and efficiency ratio (Fig. 2). Significant specific energy consumption (1189-1297 g/(kW⋅h) and 962-1147 g/(kW⋅h)) is observed at low (0.2) and maximum load of the generator.

Moreover, the closer the load to the minimum value the higher the specific costs of the unit. They are even higher than while overloading the generator. The optimal load level for electric generators of this design, at which the lowest level of specific fuel consumption is expected, is 0.7 for different types and 560 and 605 g/(kW⋅h), respectively.

The reason for these effects is a number of negative phenomena that accompany the process of electricity generation when the load deviates from the optimum level. The main reasons include, in the case of increased power, deterioration of the gas filling of the cylinder, reduction of turbulence with the charge part release from the cylinder into the inlet system with increasing fuel supply. Also fuel consumption increases in the mode close to idle due to the reactive power generation (which is required for generation at different load levels) added to the total energy consumption level of.

a

b

Fig. 2. Diagrams of changes in specific fuel consumption (a) and efficiency (b) when using different types of fuels:

――― - gasoline A-95 - Euro5; ――― - gasoline automobile A-95 - Euro5 - E7

An excessive use of fuel at low load will be typical for most generators due to the need to maintain the frequency of the internal combustion engine, which is accompanying by the cost of friction, including aerodynamic. High specific fuel consumption at the maximum load of the generator is related to deterioration of filling of cylinders and incomplete combustion of fuel. Taking into account these features, data acquisition will be characteristic for all spark ignition generators.

The established distributions of specific values of fuel consumption and the value of the energy efficiency factor for different load levels using different fuels according to the new measurement method are necessary for modeling and planning of systems energy consumption using generating units of this type.

The present study proposes a new method of determining the values of fuel consumption and the value of a power unit energy efficiency with two fuels (ethyl gasoline), which allows to monitor the maximum efficiency. Thus, for this equipment it is 0.147 and 0.138 at the load of 0.7 from nominal for different types of fuels. Specific consumption levels for optimal load are 560 and 605 g/(kWh), respectively.

Under certain conditions the use of this technique, which is based on the determination of instantaneous power values, allows to avoid significant errors (30%) in determining the energy parameters.

In addition, the experimental evaluation of the generating unit operation confirmed that the fuel without ethanol impurities allows to generate more electricity, which should be used when there is a great need.

Approaches to the formation of air-fuel mixture in the burner devices

The increase in the capacity is due to the development of autonomous power supply systems, which not only complement stationary power units, but in many cases provide solutions to important technical problems of reliability of power supply in cases of disconnection from the main grid. The implementation of this solution is possible only under conditions of high reliability and energy efficiency of power generating equipment provided by the system of technical diagnostics presented in [11-12]. This is due to the difficulty of forecasting the electricity needs of different numbers of energy consumers.

The specificity of the use of electric generators with spark ignition as backup power sources is their periodic use for long intervals. The use of gasoline in such operation is complicated due to its limited service life, which is associated with the formation of resins and a decrease in octane number. It should also be noted that the Ukrainian market is full with low quality gasoline, which significantly affects environmental issues and energy performance of power units. These shortcomings are devoid of fuels based on liquefied petroleum gases. The use of liquefied petroleum gases significantly extends the service life of equipment with lower cost of electricity generation [13]. However, there is no data for the cases of electric generators upgraded for performance on liquefied petroleum gas.

For optimal use of modernized electric generators which work on liquefied petroleum gas in autonomous power supply systems and backup power supply systems, it is necessary to investigate the equipment performance at different load levels and different types of fuels (liquefied petroleum gas and gasoline).

During the process of reviewing the papers devoted to determining the energy performance of power units based on the internal combustion engine should be grouped by two characteristics: the type of fuel and the type of power unit.

Papers considering the type of fuel can be divided into two areas: the first of which is the study of energy parameters of energy generating units that operate using renewable energy sources; the second - research of energy parameters of power generating units with a combination of fuels made of different types of fossils.

Work on the study of energy parameters of power generating units operating with the use of renewable energy sources in general is aimed at studying the peculiarities of the use of fuels of plant origin or hydrogen [14-18]. The use of hydrogen to generate electricity has great prospects, but with a higher efficiency (60-70%) in fuel cells. It should also be noted the limited availability and shelf life of plant-based fuels.

Among the papers aimed at studying the energy parameters of power generating units with a combination of fuels produced from different types of fossils, the closest to the chosen study are papers related to the use of compressed natural gas (CNG) and liquefied petroleum gas (LPG) [19-23]. It should be noted that a common feature of the use of liquefied gas is to increase fuel consumption during engine upgrades to 20%. Common features of these papers are that LPG reduces the volumetric efficiency of the engine and, thus, the effective power of the engine. In addition, the reduction in volume efficiency also reduces the effective efficiency of the engine and, consequently, increases the specific fuel consumption. Most studies have been conducted to establish energy performance depending on the speed for a narrow load range of the power unit. At the same time, studies [24] claim that the fuel conversion efficiency (FCE) increase by 2.90% leads to a decrease in specific fuel consumption by 17-18% for compressed natural gas. Analysis of [25] shows a significant increase in gasoline consumption up to 300% with the deviation from the nominal speed.

According to the type of energy generating unit, the papers are divided into: internal combustion engine as an independent element and a complex energy generating system which includes an internal combustion engine. The first type considers the process of determining energy parameters by studying mainly the characteristics of the internal combustion engine at different speeds and torques. The ratio of fuel consumption to engine power is used as an energy efficiency characteristic - brake-specific fuel consumption. This approach is based on the fact that the main losses of the units fall on the internal combustion engine. The second type of equipment involves the transfer of research on the power plant as a whole, in some cases considering the energy performance of the components of the system [16, 27]. Energy efficiency in this case is assessed by the ratio of power generated by the electric generator and fuel consumption of the engine. Also, for both groups of research for loading the internal combustion engine is connected to the electromechanical loader - an electric brake, the block of resistors or the generator.

Among the papers of the first group it is possible to note the paper on the use of mixtures of alternative fuels with mineral fuels [20]. In these articles, the influence of various factors (the ratio of biofuels with mineral fuels, gas and liquid fuels, speed, angle of advance of the spray or ignition) on the energy performance of plants is mainly investigated. The main purpose of these studies is to confirm the possible reliable and environmentally safe use of alternative fuels in the generation of electricity. A number of studies have noted the independence of unit costs from the level of power plant [28].

The work is aimed at optimizing the operation of the power plant using a mixture of fuels (hydrogen and gasoline) as factors used fuel concentration and speed of the shaft of the internal combustion engine of the generator [25]. A characteristic of the established pattern is the change of the optimal value of the efficiency at different concentrations of the fuel mixture and the load, which allows to optimize the generation process by using different mixtures. To determine the conditions that correspond to the optimal value of the efficiency, most experiments were conducted at a minimum value of 2.5 kW (<50%) and do not cover the entire possible range of variation.

The work is aimed at studying the efficiency of a spark ignition engine by converting the thermal energy of exhaust gases into electricity using a thermoelectric generator is devoted to the issue of improving the energy efficiency of the power plant [29-31]. When changing the power from 25 to 75 kW, there was no significant change in specific fuel consumption (within 3%), which differs significantly from the known data.

The original models, algorithms, software and hardware of the system developed for controlling the fuel combustion process are presented in [32-34]. These articles examine key issues in improving the efficiency of small and medium power boiler units by adding control systems for the fuel combustion process. The features of fuel combustion in the boiler do not allow direct use of the obtained results, but may be useful in planning the experiment.

The general characteristic of the presented papers includes the rarity of the combination of fuel mixtures and methods of electricity production. Quite a little attention is paid to the conditions of the experiment, the influence of engine parameters, rheological and chemical parameters of fuels. Also, the studied models of autonomous generators and motors have various applications as a backup or autonomous power sources. The question of the expediency of using liquefied gas and gasoline depending on the load of the generating unit remains open.

Given the above, it is possible to conclude that it is necessary to study the energy performance of a common type of generator, namely a synchronous generator with a spark ignition engine. Also, special attention needs to be paid to the type and conditions of fuel use, which are maximally represented on the market.

The aim of this study is to determine the energy performance of autonomous electric generators based on spark ignition engines which use the most common fuels: liquefied petroleum gas and gasoline.

Based on the analysis of the above mentioned papers, the following parameters were selected as energy indicators required for modeling the operation of autonomous power supply systems based on spark ignition engines:

- Brake Specific Fuel Consumption for the generation of electricity at different load levels (BSFC), g/kW·h;

- coefficient of efficiency at different load levels.

Two types of the most common fuels were used as fuel for the conducted experiments (according to DSTU EN 589: 2017, DSTU 7684: 2015):

- propane-butane automobile, liquefied petroleum gas (LPG) brand A;

- gasoline automobile A-95 - Euro5.

An electric generating unit based on a single-cylinder gasoline four-stroke internal combustion engine with an engine capacity of 200 cm3 was selected for the study. Technical characteristics are given in table 4. Most generators use as an alternator the synchronous generator with automatic voltage regulator (AVR), which contains the rotor and stator windings. The rotor speed of the generator is maintained by a centrifugal frequency regulator connected to the carburetor. For experiments, the engine carburetor was replaced by an upgraded carburetor with a capacity of 1.6-3 kW, which allows the use of liquefied petroleum gas, compressed natural gas and gasoline. Reducer RDSG 1.1.2 (Fig. 3) was used to reduce the pressure of the gas cylinder.

Fig. 3. Experimental plant electric generator with a spark ignition engine using liquefied petroleum gas and gasoline

The main parameters of the power generation unit are shown in Table 4.

Table 4. Composition and quantity of methane combustion products

Parameter	Unit	Value
Engine type	-	4-stroke gasoline engine with air cooling OHV
Number of cylinders	pcs	1
Engine model	-	H-168
Engine capacity	cm3	196
Engine power	W	4780
Maximum power of the generator	W	2800
Fuel tank volume	m3	0.015
The volume of the gas cylinder	m3	0.005

The BSFC at different load levels for LPG is calculated similarly by comparing the mass of the gas cylinder at the beginning and at the end of the test. The period of operation was 300 .

To facilitate the analysis of the data in Tables 5 and 6, graphs of changes in Brake Specific Fuel Consumption and efficiency (Fig. 4) were built. Significant specific energy consumption (1276; 720 g/(kW⋅h) and 1032; 384 g/(kW⋅h) is observed at low (0.2) and maximum load of the generator. The optimal load level for electric generators of this design, at which the lowest level of specific fuel consumption is expected to be 0.7 and 0.8 for different types is 610 and 342 g/(kW⋅h), respectively, due to different chemology of the fuels.

Table 5. Energy efficiency parameters of the electric generator for A-95 gasoline - Euro5

Δt, s	r, g/s	, g/J	, g/(kW·h)	η
1	0	97	0.1626	-	-	-
2	0.2	89	0.1773	0.00036	1276.7	0.068
3	0.4	70	0.2253	0.00023	811.33	0.108
4	0.6	62	0.2544	0.00017	610.68	0.143
5	0.8	44	0.3585	0.00018	720.52	0.136
6	1	21	0.7172	0.00031	1032.9	0.085

Table 5. Generator energy efficiency parameters for liquefied petroleum gas (LPG)

m, g	r, g / s	, g / J	, g/(kW·h)
1	0	27	0.09	-	-	-
2	0.2	35	0.117	0.00034	720.4	0.106
3	0.4	47	0.157	0.000133	480.2	0.160
4	0.6	55	0.183	0.000183	360.2	0.213
5	0.8	75	0.250	0.000125	342.1	0.224
6	1	96	0.320	0.000128	384.8	0.200

a

b

Fig. 4. Diagrams of changes in specific fuel consumption (a) and efficiency (b) when using different types of fuels:

――― - gasoline A-95 - Euro5;―――- propane-butane automobile, liquefied petroleum gas (LPG) brand A

When the LPG was used there was an increase in efficiency with a total of 5-7%. The maximum value of efficiency for different fuels was 14.3% and 22.4% for different load levels (0.6 and 0.8 from nominal). For certain ratios of the fuels consumption at different load ranges, it is advisable to use different types of fuels.

The increase in consumption in the mode close to idling is due to the fact that the total energy costs consumption is added to the consumption of fuel due to creating reactive power, which is necessary for generation at different load levels. At the maximum load, the reason for the deterioration of energy performance is poor gas filling and ventilation of the cylinders.

The established distributions of specific values of fuel consumption and the value of the energy efficiency factor at different values of the load using different fuels according to the new measurement method are necessary for modeling and planning energy consumption of energy systems using generating units of this type.

This section presents experimental studies to determine the energy performance of the one of the world's most common designs of electric generator performing on gasoline and liquefied petroleum gas.

Main energy indicators at using liquefied petroleum gas and gasoline chosen by the authors: specific fuel consumption and energy efficiency factor of the power unit. Significant specific energy consumption (1276; 720 g/(kW⋅h) and 1032; 384 g/(kW⋅h) are observed at low (0.2) and maximum load of the generator.

It has been determined that the highest values of efficiency of 14.3% and 22.4% for different fuel types are observed at different load levels (0.6 and 0.8). The established values of the distribution of energy indicators allow to predict the optimal parameters of autonomous units using different types of fuels at different load levels.

Determination of the technical condition of autonomous electrical energy source with internal combustion engine

Among the organizational and technical means aimed at preserving the life, health and working capacity of a person during his work, special attention is paid to a special group of electric consumers. A special group of electrical consumers is distinguished from the composition of electrical consumers of the first category of reliability, the uninterrupted operation of which is necessary to prevent emergency production stop in order to prevent the threat to human life. To prevent the threat to people lives, additional power from a third independent, mutually redundant power source is provided. The only option for additional power supply from a third independent, mutually reserve power source in case of a main grid failure is the use of standalone power generators with internal combustion engine. Among the variety of existing autonomous power generators, one of the biggest group is occupied by single-cylinder internal combustion engine generators.

The background for the energy efficient and reliable work of electrical equipment is carrying out a set of diagnostic procedures for determining the technical condition and maintenance. The main reason for the outages of power generating plants with internal combustion engines is the worn of the cylinder-piston group. One of the most advanced methods for diagnosing the impermeability of a cylinder-piston group is to measure compression using compressors and compressographs. The disadvantages of this method can be attributed to the high complexity and inaccuracy of data related to the disassembly of the engine and the qualification of specialists who perform the diagnostic process.

The disadvantages of this system are devoid in internal combustion engine diagnostic systems that use the starter current level as a diagnostic parameter [35, 36]. The data systems are based on the analysis of engines crankshaft rotation without supplying fuel in the compressor mode by measuring the current and voltage level of the starter motors.

The use of this method requires pre-known values of diagnostic parameters, which complicates the use of this method, and for the new created objects application of such diagnosis method is impossible.

Number of papers are devoted to the analysis of the starting engine parameters that can be divided into two main groups. The first examines the start-up of the engines without moving the system to a special state and describes the functional diagnostic systems. The second group involves the transfer of the system to a special state, such as compression or partial depressurization and is dedicated to the description of test diagnostic systems.

From the first group of works, paper [37] can be mentioned for its quality of description and statement of the problem among others systems. This article presents an analytical model that is useful for analyzing internal combustion engine torque and describes a control system that utilizes direct torque transmission of a motor to reduce engine torque ripple. The article proposes to use dependencies that describe the isotropic process to model the process of air compression in cylinders. The application of the proposed dependencies is possible under the condition of taking into account the real process of air compression.

Studies [38-40] represent the description of the functional diagnostic systems in which the pressure of the crankcase gases was taken as the diagnostic parameter. The application of the proposed method is possible only if experimental data for each individual engine is known.

The researches of the diagnosing process of a cylinder-piston group in a compressor mode which the electrical parameters as a diagnostic parameters presented in [41-44] and the pressure generated by the compression of air as a diagnostic parameter presented in [45-47].

In the process of the determining the currents and pressures that occur when the engine is cranked, it is important to take into account the resistances that occur due to the action of compression forces, considering the geometric parameters of the cylindrical piston group and the crank mechanism. However, it should be noted that the general resistance to rotation is influenced by a number of components, among which the main ones are: oil mixing resistance, friction in parts that rotate and move gradually, resistances from auxiliary elements of the power unit, inertia forces resistance. Determination of these components is extremely difficult because of the strong influence of the rheological and tribological properties of the system on the contact interaction elements mechanics [48]. The consideration of these components makes it almost impossible to solve the obtained systems of equations. Also, preliminary experimental studies indicate a significant influence of the flywheel, which offsets the curve of current change.

Given the above, it is possible to conclude on the need to improve the theory, methods and tools of existing methodology of diagnosing of the power equipment with internal combustion engines.

The purpose of this study is to develop a diagnostic method and a mathematical model to determine the technical state of an autonomous generator according to the main parameter of a cylinder piston group of an internal combustion engine - true collision rate.

Considering the mentioned above, to alleviate the problem, One should define the average current of the electric starter for one motor cycle - two revolutions.

In general, the energy balance equation of the diagnosis system can be written as follows

,	(3)

where - an external energy source work; - energy for the implementation of a number of internal processes during engine rotation.

The operation of external power sources in this case is based on the starter during one cycle of the engine. Given the gear ratio i:

(4)

where M ̶ starter moment; ̶ starter power; ̶ time of one engine cycle.

Starter capacity can be determined by technical documentation or by:

(5)

where- battery voltage (12V); - average current for one cycle of the engine.

Energy consumption by the internal processes during engine rotation is the energy consumption during the friction of the parts and energy consumption by thermodynamic gas processes :

.	(4)

The energy consumption of generator rotation can be neglected due to the engine start frequency, which is within 5% of nominal generator speed.

The energy consumption due to the parts friction is based on a number of components that are associated with the piston stirring, crankshaft rotation, oil pump operation, gas distribution. The energy consumption due to the parts friction can be determined when starting the engine without the spark plug on:

(5)

where- starter current without a spark plug.

The level of energy consumption due to the gas thermodynamic processes is in air compression with heat emission. From the known dependence of thermodynamic processes of gas flow efficiency indicator is equal to:

,	(6)

where - efficiency indicator:

,	(7)

where - experimental coefficient ; – engine compression.

Polytropic compression:

(8)

where - initial pressure in the cylinder; - initial volume in the cylinder; - final volume in the cylinder; - polytropic indicator for air (1.2-1.365); ratio is the level of the engine compression.

Substituting the dependence (5-8) in (4) and assuming the equality of the coefficients , we obtain the equation energy balance of the diagnosis system:

(9)

Determine the rate of engine compression :

.	(10)

The solution of equation (9) to the engine compression rate allows to determine the residual life of the engine and to determine the energy efficiency of the generator by comparison method.

For the analysis we introduce the substitution in the solution obtained (10) used the currents ratio:

.	(11)

The currents ratio in the accepted system of diagnosis serves as an informative criterion that relates the two states of the system.

After substitution (11), decision (10) takes the form.

.	(12)

Fig. 5 presents a graph of the compression ratio on the current ratios dependence for the generator with the following parameters: ; ; ; ; .

Fig. 5. Graph of changes in compression ratio from the currents ratio

The analysis of the graph shows that the change of the compression ratio to currents ratio is inversely proportional.

The basis for obtaining reliable data is to create a permanent environment for the experiment. For the case of a standalone electric generator, the condition for the permanent environment is the internal combustion engine temperature. The friction resistance in the elements changes significantly with the change of this factor. Due to this fact, the engine was warmed up for 5 minutes before the beginning of each experiment.

After preparation of the standalone electric generator, the fuel supply to the engine was stopped.

The experimental stand for the diagnostic process of the autonomous generator is shown in Fig. 6.

The first parameter that was measured was the generator starting current (average current per engine cycle). The graph of current change is presented in Fig.7 (blue line). The average value of the starting current of the generator was .

Fig. 6. Experimental stand for diagnosing autonomous power supply

After measuring the starting current with the spark plug, the spark plug was removed and the starter rotation current was measured Fig. 7 (red line). Average current value of generator scroll was .

Fig. 7. The graph of current change

To determine the values of the compression ratio and the energy efficiency coefficient its necessary to set engine parameters. Based on the passport of the experimental unit Honda GX 200: ; ; ; .

After substitution of the current ratio into the expression for the coefficient of compression (12) the diagnostic parameter will be.

It should be noted that the passport values of the compression ratio for this engine model is 9 units. The error value of the proposed method is in the range of 2.2%.

A simulation model of diagnosing process of the autonomous electric generator with internal combustion engine is developed. The developed simulation model of diagnosis process allows to determine the compression level of generator from the starting currents. The proportional dependence of the change in the compression coefficient to currents ratio coefficient is established. The difference between obtained experimental values with passports values is 2.2%, which indicates the sufficiently high accuracy of the proposed diagnostic method.

References

V. Bilodid, K. Taranets, “Investigation of the model of functioning of production and technological potential of subway power supply departments,” Problems of general energy, 2008, pp. 40-47.

S. Ermilov, “Energy strategy of Ukraine for the period up to 2030: problematic issues of content and implementation," Mirror of the week, vol. 20, 2006.

Zaichenko, S. Shevchuk, R. Kulish, S. Denysiuk, D. Derevianko and Opryshko, “Identification of the least reliable elements of autonomous power plant based on internal combustion and diesel engines by the method of the lowest residual entropy,” In 2021 IEEE 2nd KhPI Week on Advanced Technology (KhPIWeek), vol. 1, pp. 549-552, September 2021.

S. Zaichenko, S. Shevchuk, R. Kulish, S. Denysiuk, D. Derevianko and V. Opryshko, “Identification of the least reliable elements of autonomous power plant based on internal combustion and diesel engines by the method of the lowest residual entropy , ”In 2021 IEEE 2nd KhPI Week on Advanced Technology (KhPIWeek), vol. 1, pp. 549-552, September 2021.

A. Irimescu, G. Vasiu, “Performance and emissions of a small scale generator powered by a spark ignition engine with adaptive fuel injection control,” Applied Energy, 2014, pp. 196-206.

M. Rebai, S. Kelouwani, Y. Dubé and F. Agbossou, “Low-Emission Maximum-Efficiency Tracking of an Intelligent Bi-Fuel Hydrogen – Gasoline Generator for HEV Applications,” In IEEE Transactions on Vehicular Technology, 67 (10) , 2018, pp. 9303-9311.

A. Reddy, M. Shankar, K. Apparao, “Experimental determination of brake thermal efficiency and brake specific fuel consumption of Diesel engine fueled with Bio-Diesel,” International Journal of Engineering and Technology, 2 (5), 2010, pp. 305-309.

R. Crookes, “Comparative bio-fuel performance in internal combustion engines,” Biomass and Bioenergy, 30 (5), 2006, pp. 461-468.

I. Surata, T. Nindhia, I. Atmika, D. Negara, and I. Putra, “Simple conversion method from gasoline to biogas fueled small engine to powered electric generator,” Energy Procedia, 52, 2014, pp. 626-632.

D. Onishchenko, S. Pankratov, A. Zotov, A. 'Osipkov and R. Poshekhonov Study of the influence of hydraulic thermoelectric generator resistance on gasoline engine efficiency, ”International journal of applied engineering research, 12 (5), 2017, pp. 721-727.

I. Kulbovskyi, H. Holub, V. Kyiashko, O.Gurenkova, V. Kharuta, ‘Investigation of the model of functioning of production and technological potential of subway power supply departments,” Transport Means - Proceedings of the International Conference, 2020, pp. 416–420.

Transport Means - Proceedings of the International Conference, 2020, стр. 416–420S. Zaichenko, S. Shevchuk, R. Kulish, S. Denysiuk, D. Derevianko and V. Opryshko, “Identification of the least reliable elements of autonomous power plant based on internal combustion and diesel engines by the method of the lowest residual entropy,” In 2021 IEEE 2nd KhPI Week on Advanced Technology (KhPIWeek), vol. 1, pp. 549-552, September 2021.

S. Zaichenko, S. Shevchuk, V. Opryshko, S. Pryadko, A. Halem and A. Adjebi, “Determination of autonomous electrical energy source technical condition based on an internal combustion engine,” In 2020 IEEE 2nd KhPI Week on Advanced Technology (KhPIWeek), vol. 1, pp. 305-308, October 2020.

A. Lisoval “Rezul'taty issledovanij po primeneniyu smesi biogas i metana v gazovom dvigatele elektrostanii,“ Dvigateli vnutrennego sgoraniya, vol. 2, 2020, pp. 58-63.

M. Rebai, S. Kelouwani, Y. Dubé and F. Agbossou, “Low-Emission Maximum-Efficiency Tracking of an Intelligent Bi-Fuel Hydrogen – Gasoline Generator for HEV Applications,” In IEEE Transactions on Vehicular Technology, 67 (10) , 2018, pp. 9303-9311.

A. Reddy, M. Shankar, K. Apparao, “Experimental determination of brake thermal efficiency and brake specific fuel consumption of Diesel engine fueled with Bio-Diesel,” International Journal of Engineering and Technology, 2 (5), 2010, pp. 305-309.

R. Crookes, “Comparative bio-fuel performance in internal combustion engines,” Biomass and Bioenergy, 30 (5), 2006, pp. 461-468.

I. Surata, T. Nindhia, I. Atmika, D. Negara, and I. Putra, “Simple conversion method from gasoline to biogas fueled small engine to powered electric generator,” Energy Procedia, 52, 2014, pp. 626-632.

Crookes, RJ (2006). Comparative bio-fuel performance in internal combustion engines. Biomass and Bioenergy, 30 (5), 461-468.

I. Surata, T. Nindhia, I. Atmika, D. Negara and I. Putra, “Simple conversion method from gasoline to biogas fueled small engine to powered electric generator,” Energy Procedia, 52, 2014, pp.626-632.

H. Bayraktar, O. Durgun, “Investigating the effects of LPG on spark ignition engine combustion and performance,” Energy conversion and management, 46 (13-14), 2005, pp. 2317-2333.

B. Erkus, A. Surmen and M. Karamangil, “A comparative study of carburation and injection fuel supply methods in an LPG-fueled SI engine,” Fuel, 107, 2013, pp. 511-517.

M. Aslam, H. Masjuki, M. Kalam and M. Amalina, “An experimental investigation of CNG as an alternative fuel for a retrofitted gasoline vehicle,” Fuel, 85 (5-6), 2006, pp. 717-724.

E. Dai, M. Lin, J. Xia and Y. Dai, “Experimental investigation on a GAX based absorption heat pump driven by hybrid liquefied petroleum gas and solar energy,” Solar Energy, 169, 2018, pp.167-178.

A. Demirbas, “Fuel properties of hydrogen, liquefied petroleum gas (LPG), and compressed natural gas (CNG) for transportation,” Energy Sources, 24 (7), 2002, pp. 601-610.

M. Masi, “Experimental analysis on a spark ignition petrol engine fueled with LPG (liquefied petroleum gas),” Energy, 41 (1), 2012, pp. 252-260.

M. Aslam, H. Masjuki, M. Kalam, H. Abdesselam, T. Mahlia and M. Amalina, “An experimental investigation of CNG as an alternative fuel for a retrofitted gasoline vehicle,” Fuel, 85 (5-6), 2006, 717-724.

E. Dai, M. Lin, J. Xia, and Y. Dai, “Experimental investigation on a GAX based absorption heat pump driven by hybrid liquefied petroleum gas and solar energy,” Solar Energy, 169, 2018, pp. 167-178.

S. Zaichenko, S. Shevchuk, V. Opryshko, S. Pryadko and A. Halem, “Autonomous electric power source energy efficiency improvement by internal combustion engine gases distribution control,” In 2020 IEEE 7th International Conference on Energy Smart Systems (ESS) , pp. 262-265, May 2020.

A. Irimescu, G. Vasiu and G. Tordai, “Performance and emissions of a small scale generator powered by a spark ignition engine with adaptive fuel injection control,” Applied energy, 121, 2014, pp. 196-206.

D. Onishchenko, S. Pankratov, A. Zotov, A. 'Osipkov and R. Poshekhonov Study of the influence of hydraulic thermoelectric generator resistance on gasoline engine efficiency, ”International journal of applied engineering research, 12 (5), 2017, pp. 721-727.

A.O. Zaporozhets. Research of the Process of Fuel Combustion in Boilers. Control of Fuel Combustion in Boilers. Studies in Systems, Decision and Control. - 2020. - vol 287. - pp. 35-60. doi: 10.1007/978-3-030-46299-4_2

A.O. Zaporozhets. Methods and Means for the Control of the Fuel Combustion Process. Control of Fuel Combustion in Boilers. Studies in Systems, Decision and Control. - 2020. - vol 287. - pp. 1-33. doi: 10.1007/978-3-030-46299-4_1

V.P. Babak, S.V. Babak, M.V. Myslovych, A.O. Zaporozhets, V.M. Zvaritch. Technical Provision of Diagnostic Systems. Diagnostic Systems For Energy Equipments. Studies in Systems, Decision and Control. - 2020. - vol. 281. - pp. 91-133. doi: 10.1007/978-3-030-44443-3_4

K. Tymanyuk, V. Kostenko Development of an automated system for iterative control of the technical condition of a car engine system. Technological audit and production reserves, (1 (2)), pp. 77-82, 2016.

A. Baboshin. Evaluation of the technical condition of engines by the current consumed by the starter when the engine scrolls, Bulletin of Murmansk State Technical University, vol. 16 (1), pp. 33-39, 2013.

S. Shevchuk, S. Zaichenko, V. Opryshko, A. Adjebi, Determination of the diagnostic system inertial parameters for power generating station combustion engine, Paper presented at the 2019 IEEE 6th International Conference on Energy Smart Systems, ESS 2019 - Proceedings, pp. 88-91, 2019.

R. Davis, R. Lorenz, Engine torque ripple cancellation with an integrated starter alternator in a hybrid electric vehicle: implementation and control, IEEE Transactions on Industry Applications, vol. 39(6), pp. 1765-1774, 2013.

A. Baboshin, A. Kosarev, V. Malyshev Evaluation of the technical condition of internal combustion engines by pressure in the intake and exhaust manifolds, Bulletin of the Murmansk State Technical University, vol. 3, pp. 23-32, 2013.

A. Baboshin, V. Malyshev, Development of a method for the integrated diagnosis of engines and devices for assessing the technical condition of the piston part of the internal combustion engine, Bulletin of the murmansk state technical university, vol. 4/2., pp. 925-930, 2010.

A. Bazhinov, E. Serikova, Software and hardware complex for estimating the residual life of an internal combustion engine, Bulletin of kharkov national automobile and highway university. vol. 45, pp. 25-31, 2009.

M. Averbukh, B. Rivin, J. Vinogradov, On-Board Battery Condition Diagnostics Based on Mathematical Modeling of an Engine Starting System, SAE Transactions, vol. 1476, pp. 406-413, 2007.

V. Nechaev, V. Kapustin, I. Korablin, An indiscriminate method for determining the state of a cylinder-piston engine group by the spread of compression, Science, Education and Innovation in the Modern World, vol. 7, pp. 346-352, 2018.

V. Nechaev, E. Vorobev, A. Tarasenko, Techniques for the technical diagnosis of a cylinder-piston group of diesels by cold cranking the crankshaft, Engineering Bulletin of the Don, vol. 3 (50), pp. 31-39, 2018.

S. Krivtsov, Y. Ukkunov, T. Krivtsova, Theoretical background of the method for diagnosing the compression properties of a diesel engine by current parameters, Bulletin of Irkutsk State Agricultural Academy. vol. 38, pp. 71-77, 2010.

S. Krivtsov, A. Pukalo, T. Krivtsova, Comparison of the diagnostic parameters for evaluating the tightness of the piston space of the diesel engine cylinders when the starter scrolls without fuel supply, Automotive Engineers Journal, vol. 6, pp. 54-57, 2015.

S. Kukov, A. Gritsenko, D. Bakaykin Improving the process of diagnosing a cylinder-piston group, Materials LV Intern. scientific and technical Conf. "Achievements of Science –Agricultural Production". Chelyabinsk: FSBEI of the South Ural State Agrarian University, vol. 1, pp. 77-82, 2016.

O. Larin, S. Kukov, A. Gritsenko, K. Glemba, 2016. Diagnostic results of the cylinder-piston group by the method of assessing dynamic compression, Agribusiness of Russia, vol. 23(3), pp. 619-625, 2016