Підвищення енергетичної ефективності робочих машин з отто-двигунами засобами hard-soft-технології

Abstract

Розглядається технологія моделювання/дослідження явищ теплотворення, тепловіддачі, тепловикористання у тепловій машині швидкого внутрішнього згоряння (отто-двигуні), в основу якої покладено принципи праксеологічності. Зазначено, що подальший розвиток класичних підходів до моделювання робочих процесів у двигуні, спираючись суто чи здебільшого на аналітико-алгоритмічні описи, є практично неможливим. Тож запропоновано залучити в модель також і реальний робочий простір двигуна, системно приєднуючи його до віртуального, втіленого в програмно-алгоритмічному середовищі, і тим самим впроваджуючи частину реальності в модель цієї ж реальності. Потрібної ефективності моделі надає імітація в програмному середовищі взаємодії між собою і довкіллям двох зон, на які поділено модельний робочий простір двигуна. Саме у разі двозонного трактування модельного робочого простору стає можливим відмовитись від аналітичного контролю за хімічною рівновагою в робочому середовищі і не існує причин, які б зумовлювали речовинний обмін між зонами. Рассматривается технология моделирования/исследования явлений теплообразования, теплоотдачи, теплопотребления в тепловой машине быстрого внутреннего сгорания (отто-двигателе), в основание которой положены принципы праксеологичности. Признано, что последующее развитие классических подходов к моделированию рабочих процессов в двигателе, опираясь сугубо или по большей части на аналитико-алгоритмические описания, является практически невозможным. Поэтому предложено привлечь в модель также и реальное рабочее пространство двигателя, системно присоединяя его к виртуальному, воплощенному в программно-алгоритмической среде, и тем самым внедряя часть реальности в модель этой же реальности. Необходимую эффективность модели обеспечивает имитация в программной среде взаимодействия между собой и окружающей средой двух зон, на которые разделено модельное рабочее пространство двигателя. Именно в случае двухзонной трактовки модельного рабочего пространства становится возможным отказаться от аналитического контроля за химическим равновесием в рабочей среде и не существует причин, которые бы обуславливали обмен веществами между зонами. We consider a technology for modeling/studying phenomena of heat formation, heat transfer, heat utilization in the engine of rapid internal combustion, underlying which are the principles of praxeology. It is recognized that further development of classic approaches to modeling working processes in the engine relying purely or mainly on the analytical-algorithmic descriptions is almost impossible. It is therefore proposed to additionally introduce to the model an actual workspace of the engine, systemically connecting it to the virtual, implemented in the software-algorithmic environment, thereby introducing part of the reality to the model of the same reality. Within the framework of this study, we used, as a full-scale workspace, a cylinder from the tested engine BRIGGS&STRATTON, mounted at a special test bench. In this case, there is a possibility to greatly simplify the analytical component of the modeling representation of working processes in the engine, building it on the basis of classical analytical ratios that reflect the law of conservation of matter, the law of preservation of energy, a heat transfer law, as well as equations of thermodynamic state of a working body. The model acquires specificity not due to special empirical descriptions, but by acquiring current information from the real information space based on the principles of similarity theory. The required effectiveness of the model is provided by a simulation in the programming environment of interaction amongst itself and the environment of two zones into which a modeled engine workspace is split. A dual-zone model is opposed to the so-called multi-zone models, within which there is always a high risk of errors, almost uncontrolled, which require a complex and labor-intensive information support and maintenance. It is in the case of a two-zone representation of the modelled working space that it becomes possible to abandon the analytical control over chemical equilibrium in a working environment and there are no reasons that would predetermine the exchange of substances between zones. Therefore, it becomes possible to determine heat transfer to the walls of a working space similar to a single-zone model. It follows from the study conducted that it is expedient to apply a exponential heat-generating function (Wiebe function) for the virtual simulation of a heat formation phenomenon. Quality of simulation is improved by acquiring information obtained in the process, so to speak, of "on-line communication" between a virtual (in the form of software) and an actual (in the form of a full-scale workspace) parts of the modeling environment. In general, the course of heat generation process is commonly characterized by the index m>0 of fuel burn-out quality and the index of capacity of combustion. This approach to the identification of processes in the internal combustion engines appeared to be rather effective. As a rule in case of analytical identification of heat generation – heat consumption processes the index a of combustion capacity is defined in advance. The acquired information, however, demonstrates that there are more reasons to consider the value of the parameter m to be set in advance, rather than of the parameter a. The relation between values of heat emission maximal intensiveness  z and the time of its achievement  in an empirical sense is seemingly parabolic. Theoretically, as it has been found out, it can be evidently treated as “fuzzy” hyperbolic. The fact that the engine’s idle run does not conform to the “hyperbolic” tendency manifests its considerable imperfection and does not contend against the theoretically substantiated regularity. Given, for example, that 1    z , it is possible to acknowledge that 93, 1  m . While given 2  m , we will have to acknowledge that 03, 1    z . Thus, if we assign in advance that a=–6,908 (as usual) we considerably limit the flexibility and preciseness of the identification algorism. Equation of forced convection is traditionally based on a similarity relationship m n C Pr Re Nu = between criteria Nusselt (Nu), Reynolds (Re), Prandtl (Pr); C, n, m, — constant. G. Woschni found out that the values of the degrees of power are acceptable m=0,78 and n=0,33. But in general it turned out that good simulation results can be obtained on the basis of experimental information on the flow of pressure and average temperature in the engine cylinder, taking n=1/3 and for each mode of operation of the engine its meaning m from the range 3/4<m<4/5. Examples of model reproduction of the change in the coefficient of heat output from the angle of rotation of the motor shaft for different loads are given. The presentation of the material is accompanied by illustrative material, which reflects information, obtained by modeling tools, about a change in: the working pressure in the engine working space, the temperature of a working body, an excess air coefficient, a heat transfer coefficient. We also included examples of change in the intensity of heat formation and intensity of heat transfer at the surface of: the working space in general, a cylinder liner, a cylinder lid, a piston head. Among the illustrations are the characteristics of the internal (intra-zone) heat exchange.