СРАВНИТЕЛЬНЫЙ АНАЛИЗ РАБОТЫ БЕНЗИНОВОГО И ВОДОРОДНОГО ДВС

УДК 62-1/-9

Abstract

The current role of the global transport system and the tightening of environmental requirements have been defined. Promising directions for the use of hydrogen in transport, as well as problematic issues of direct hydrogen use in internal combustion engines (ICEs), have been identified. Attention has been focused on the physicochemical properties of traditional fuel and the promising hydrogen source, as differences in fuel characteristics alter the processes of mixture formation, ignition, and combustion. A systems analysis was applied in the study to consider ICEs as complex, integrated energy power systems. A comparison of the engines under consideration was carried out based on systemic criteria: energetics, thermodynamics, ecology, operational aspects, design, economics, and safety. The operating cycles of H₂ and gasoline engines were examined, and characteristic features of both types of power systems were established. A detailed analysis of adaptations for hydrogen ICEs was performed, indicator diagrams were constructed, and their comparisons were made based on various parameters. The main positive and negative characteristics of both types of power plants were analyzed, including an analysis of fuel injection into the cylinder and factors accompanying this process. A constructive comparison was made from the perspective of fuel jet physics. Engineering and operational aspects of the comparison are presented. The prospects for the development of hydrogen ICEs in transport are considered. Factors hindering the development of H₂-ICEs have been identified.

Аннотация

Определена текущая роль мировой транспортной системы и ужесточение экологических требований. Выявлены перспективные направления использования водорода на транспорте, а также проблемные вопросы прямого использования водорода в двигателях внутреннего сгорания (ДВС). Акцентировано внимание на физико-химические свойства традиционного топлива и перспективного источника водорода, поскольку различия в характеристиках топлив меняют процессы смесеобразования, воспламенения и горения. В ходе исследования применен системный анализ для рассмотрения ДВС как сложной, комплексной энергетической силовой системы. Осуществлено сравнение рассматриваемых двигателей по системным критериям: энергетика, термодинамика, экология, эксплуатационный аспект, конструкция, экономика, безопасность. Рассмотрены рабочие циклы Н₂ и бензинового двигателей, установлены характерные особенности обоих типов силовых систем. Проведен детальный анализ приспособлений для водородного ДВС, построены индикаторные диаграммы и осуществлены их сравнения по различным параметрам. Проанализированы основные положительные и отрицательные характеристики обоих типов силовых установок, в том числе анализ впрыска топлива в цилиндр и факторы, сопутствующие данному процессу. Осуществлено конструктивное сравнение исходя из позиций физики струи топлива. Показаны инженерные и эксплуатационные аспекты сравнения. Рассмотрены перспективы развития водородного ДВС на транспорте. Сформированы факторы, сдерживающие развитие Н₂-ДВС.

Keywords: transport system, ecology, hydrogen in transport, internal combustion engines, system criteria, H₂-ICE.

Ключевые слова: транспортная система, экология, водород на транспорте, ДВС, системные критерии, Н₂-ДВС.

Introduction

Internal combustion engines running on traditional fuels remain the backbone of global transport infrastructure. However, increasingly stringent environmental regulations and the need to reduce carbon dioxide emissions are driving the search for alternative fuels [1; 2].

The use of hydrogen as an energy carrier is considered one of the most promising areas [3]. A hydrogen internal combustion engine (H₂-ICEs) is a modification of the traditional internal combustion engine in which hydrogen is used instead of hydrocarbon fuel, while the four-stroke cycle principle is retained.

Despite structural similarities, the physicochemical properties of gasoline and hydrogen differ significantly [4], leading to changes in the nature of mixture formation, ignition, and combustion processes [5].

Materials and Methods

The study drew upon academic literature, published open-access materials, research institution bulletins, scholarly articles, and online resources. Given their complexity, the comparison between gasoline and hydrogen internal combustion engines (ICEs) was conducted using a systems analysis approach, treating them as systems of interconnected elements. Data from various fields of knowledge were integrated, and the engines under study were analyzed as complex energy systems. The comparison was based on a set of systemic criteria: energy performance, thermodynamics, environmental impact, operational aspects, design, economics, safety, and infrastructure availability.

Results and Discussion

Energy parameters indicate the characteristics of energy conversion from fuel, volumetric density, and the efficiency of the internal combustion engine.

Thermodynamic criteria characterize the engine cycle. For example, the Otto cycle comprises four sequential strokes: 1. intake; 2. compression; 3. power stroke; 4. exhaust.

The thermodynamic efficiency of the cycle is determined by the compression ratio:

η=1-1/ε^(γ-1)

η — thermal efficiency; ε — compression ratio; γ — adiabatic exponent of the working fluid.

The operating cycle of a hydrogen engine comprises the following strokes: intake, compression, power, and exhaust.

During the intake stroke, hydrogen mixes rapidly and uniformly with air. However, the low density of the gas reduces the cylinder volumetric efficiency [6].

The compression stroke is characterized by a high tendency for the mixture to undergo pre-ignition.

The power stroke is accompanied by the very rapid combustion of hydrogen. Consequently, pressure rises rapidly, combustion is complete, heat losses are reduced, and thermal efficiency increases.

Exhaust stroke: the primary product of hydrogen combustion is H₂O. However, at high combustion chamber temperatures, atmospheric nitrogen reacts with oxygen to form nitrogen oxides (NOₓ) [7].

Characteristic features of a hydrogen engine include a more rapid pressure rise, an earlier peak pressure, and a significantly faster flame front propagation.

A hydrogen engine produces virtually no carbon dioxide, as the fuel contains no carbon [8].

The comparison of internal combustion engine indicator diagrams is carried out based on several parameters: diagrams 1 and 2.

Table 1. Comparison of indicated parameters for gasoline and H₂-ICE engines

A comparison of the key parameters of the compression-ignition and expansion strokes demonstrates the energy advantage of the H₂-ICE.

Furthermore, the injection of gasoline and hydrogen into the internal combustion engine cylinders occurs according to the characteristics specific to each fuel type [9]. In a gasoline engine, injection begins prior to Top Dead Center (TDC); fuel particles evaporate relatively slowly; the formation of the fuel cloud takes longer; inertial droplet motion is observed; and phenomena such as "wall wetting" and film formation occur. Relevant factors include injector pressure, fuel droplet size, air temperature, in-cylinder turbulence, combustion chamber geometry, injector spray angle, gasoline volatility, and in-cylinder pressure.

In hydrogen internal combustion engines, injection occurs close to Top Dead Center (TDC); phenomena observed include very high jet propagation speeds, rapid diffusive mixing, the formation of "ultra-lean" zones, and an increased risk of localized pre-ignition. Relevant factors include hydrogen storage pressure, injector opening speed, choked flow conditions, high gas diffusivity, cylinder wall temperature, spark plug location, injection timing, turbulence and swirl, and the risk of backfire and detonation.

At the same time, these engines possess a number of positive and negative characteristics. The advantages of hydrogen internal combustion engines  include the absence of CO₂ emissions, high combustion speed, high potential efficiency (around 50%), the capability for "ultra-lean burn" operation, rapid refueling compared to battery electric vehicles, and the possibility of adapting existing internal combustion engines. Disadvantages include a high risk of pre-ignition and backfire, the complexity of hydrogen storage [10], low volumetric energy density, increased NOx formation at high temperatures, and the need for expensive direct-injection fuel injectors.

The positive characteristics of the gasoline internal combustion engine include: inexpensive fuel, ease of storage, high energy density, and well-developed infrastructure. Negative aspects include: high CO₂ emissions, lower thermal efficiency (around 35%), constraints imposed by environmental regulations, and resource depletion.

A constructive comparison reveals the following: gasoline is a liquid fuel characterized by droplet breakup, where evaporation and "wall wetting" are significant factors and the mixing process is relatively slow. Hydrogen is a gaseous fuel characterized by very rapid jet penetration, strong diffusion, and a high mixture formation rate, while being extremely sensitive to injection timing. Hydrogen direct injection requires significantly higher precision in injection control compared to gasoline internal combustion engines.

The engineering and operational aspects of the comparison also have their own specific features. The advantages of H₂-ICEs include reduced carbon dioxide emissions, the possibility of retrofitting existing internal combustion engines, high efficiency, and reduced dependence on petroleum products.

However, H₂-ICEs have specific limitations and challenges. For instance, hydrogen storage requires cryogenic systems, high-pressure tanks, and special composite materials. Hydrogen embrittlement: hydrogen can penetrate metal structures and degrade the mechanical properties of materials. Increased explosion risk: the wide flammability range and low ignition energy necessitate complex safety systems. Table 2 shows components specific to the hydrogen engine.

Table 2. Devices for hydrogen internal combustion engines

At the same time, in terms of future potential, H₂-ICEs are viewed as an intermediate technology bridging the gap between traditional engines and fully electric or hydrogen fuel cell power systems. The most promising areas of application include freight transport, railway equipment, mining machinery, autonomous power units, and heavy-duty specialized equipment; unlike other forms of transport, these operate under heavy loads with virtually no downtime, and the significant financial costs involved are quickly recouped.

Conclusion

The results demonstrate that gasoline and hydrogen internal combustion engines share a common mechanical foundation and operate on the same four-stroke cycle. It was found that differences in the physical properties of the fuels radically alter the processes of mixture formation, ignition, and combustion. Analysis of the data indicates that significant modification of the conventional gasoline internal combustion engine is required to adapt it for hydrogen use. Comparing the study results with the data presented in the methodology revealed specific characteristics of modernizing existing internal combustion engines; this expands current understanding of how to address the issue at hand, including the reduction of CO₂ emissions and the improvement of thermal efficiency. These aspects necessitate design modifications to the engine, as well as the exploration of new materials and technologies. Furthermore, significant engineering challenges-such as hydrogen storage, operational safety, and nitrogen oxide formation-remain major obstacles to the widespread adoption of hydrogen-fueled internal combustion engines.

Thus, the hydrogen engine represents not a complete replacement for the traditional internal combustion engine, but a promising avenue for the development of transport propulsion technologies capable of reducing environmental impact while preserving the fundamental design principles of power units. The practical significance of this work lies in the potential to use the obtained results to improve both types of propulsion systems.

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