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HP vs BHP. You are bound to have stumbled upon the term Horsepower, whether you own a vehicle or not. HP is a measurement which is. brake horsepower (bhp) performance .. A compression ratio is the relationship between the cylinder volume .. Answer the following questions on a separate. Tag Archives: Brake horsepower This relationship between variables involved in pump performance (such as head, flow rate, shaft In this article, pump performance curve is further detailed and we will answer the following two questions.
Because of this, the committee recommends that the fuel economy information sticker on new cars and trucks should include fuel consumption data in addition to the fuel economy data so that consumers can be familiar with this fundamental metric since fuel consumption difference between two vehicles relates directly to fuel savings.
The fuel consumption metric is also more directly related to overall emissions of carbon dioxide than is the fuel economy metric.
These internal combustion engines are of two types: The discussion also addresses alternative power trains, including hybrid electrics.
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Basic Engine Types Gasoline engines, which operate on a relatively volatile fuel, also go by the name Otto cycle engines after the person who is credited with building the first working four-stroke internal combustion engine.
Over the years, variations of the conventional operating cycle of gasoline engines have been proposed. A recently popular variation is the Atkinson cycle, which relies on changes in valve timing to improve efficiency at the expense of lower peak power capability. This report uses the generic term compression-ignition engines to refer to diesel engines. The distinction between these two types of engines is changing with the development of engines having some of the characteristics of both the Otto and the diesel cycles.
Although technologies to implement homogeneous charge compression ignition HCCI will most likely not be available until beyond the time horizon of this report, the use of a homogeneous mixture in a diesel cycle confers the characteristic of the Otto cycle.
Likewise the present widespread use of direct injection in gasoline engines confers some of the characteristics of the diesel cycle. In a conventional vehicle propelled by an internal combustion engine, either SI or CI, most of the energy in the fuel goes to the exhaust and to the coolant radiatorwith about a quarter of the energy doing mechanical work to propel the vehicle.
This is partially due to the fact that both engine types have thermodynamic limitations, but it is also because in a given drive schedule the engine has to provide power over a range of speeds and loads; it rarely operates at its most efficient point. This is illustrated by Figure 2.
It plots the engine efficiency as functions of torque and speed. The plot in Figure 2. Reprinted with permission from Heywood One way to improve efficiency is to use a smaller engine and to use a turbocharger to increase its power output back to its original level. This reduces friction in both SI and CI engines as well as pumping losses. Other methods to expand the high-efficiency operating region of the engine, particularly in the lower torque region, are discussed in Chapters 4 and 5.
As discussed in Chapter 6part of the reason that hybrid electric vehicles show lower fuel consumption is that they permit the internal combustion engine to operate at more efficient speed-load points. The monitoring of engine and emission control parameters by the onboard diagnostic system identifies emission control system malfunctions. A more recent development in propulsion systems is to add one or two electrical machines and a battery to create a hybrid vehicle.
Such vehicles can permit the internal combustion engine to shut down when the vehicle is stopped and allow brake energy to be recovered and stored for later use. Hybrid systems also enable the engine to be downsized and to operate at more efficient operating points.
Although there were hybrid vehicles in production in the s, they could not compete with conventional internal combustion engines. What has changed is the greater need to reduce fuel consumption and the developments in controls, batteries, and electric drives. Hybrids are discussed in Chapter 6but it is safe to say that the long-term future of motor vehicle propulsion may likely include advanced combustion engines, combustion engine-electric hybrids, electric plug-in hybrids, hydrogen fuel cell electric hybrids, battery electrics, and more.
The challenge of the next generation of propulsion systems depends not only on the development of the propulsion technology but also on the associated fuel or energy infrastructure.
The large capital investment in manufacturing capacity, the motor vehicle fleet, and the associated fuel infrastructure all constrain the rate of transition to new technologies. A more detailed explanation is provided in Chapter 4 of this report.
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Page 16 Share Cite Suggested Citation: Thus, combustion characteristics have little effect on the ability of this type of engine to operate successfully at high speeds. Therefore, this type of engine tends to have high power density e.
CI engine combustion is governed largely by means of the processes of spray atomization, vaporization, turbulent diffusion, and molecular diffusion. Therefore, CI combustion, in comparison with SI combustion, is less impacted by engine speed.
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As engine speed increases, the combustion interval in the crank-angle domain also increases and thus delays the end of combustion. This late end of combustion delays burnout of the particulates that are the last to form, subjecting these particulates to thermal quenching.
The consequence of this quenching process is that particulate emissions become problematic at engine speeds well below those associated with peak power in SI engines. This ultimately limits the power density i. While power density gets much attention, torque density in many ways is more relevant.
Thermal auto ignition in SI engines is the process that limits torque density and fuel efficiency potential. This type of combustion is typically referred to as engine knock, or simply knock.
If this process occurs prior to spark ignition, it is referred to as pre-ignition. This is typically observed at high power settings.
Knock and pre-ignition are to be avoided, as they both lead to very high rates of combustion pressure and ultimately to component failure. While approaches such as turbocharging and direct injection of SI engines alter this picture somewhat, the fundamentals remain. CI diesel engines, however, are not knock limited and have excellent torque characteristics at low engine speed.
That is, at equal engine displacement, the turbocharged diesel tends to deliver superior vehicle launch performance as compared with that of its naturally aspirated SI engine counterpart.
Engine efficiencies have improved due to better fuels, and refineries are able to provide the fuels demanded by modern engines at a lower cost. Thus, the potential for fuel economy improvement may depend on fuel attributes as well as on engine technology. Implementing certain engine technologies may require changes in fuel properties, and vice versa. Although the committee charge is not to assess alternative liquid fuels such as ethanol or coal-derived liquids that might replace gasoline or diesel fuels, it is within the committee charge to consider fuels and the properties of fuels as they pertain to implementing the fuel economy technologies discussed within this report.
Simple geometric relationships show that an engine cylinder with longer stroke-to-bore ratio will have a smaller surface area exposed to the combustion chamber gasses compared to a cylinder with shorter stroke-to-bore ratio.
Difference Between HP and BHP | Difference Between | HP vs BHP
The smaller area leads directly to reduced in-cylinder heat transfer, increased energy transfer to the crankshaft and, therefore, higher efficiency.
Cylinder scavenging—a two-stroke phenomenon in which the exhaust products in the cylinder are replaced by fresh air—is also strongly affected by the stroke-to-bore ratio in a uniflow-scavenging, opposed-piston, two-stroke engine.
As the stroke-to-bore ratio increases, so does the distance the fresh air has to travel between the intake ports at one end of the cylinder and the exhaust ports at the other end. This increased distance results in higher scavenging efficiency and, as a result, lower pumping work because less fresh air is lost via charge short circuiting. Engine friction is affected by the stroke-to-bore ratio because of two competing effects: As the stroke-to-bore ratio decreases, the bearing friction increases because the larger piston area transfers larger forces to the crankshaft bearings.
At Achates Power, we have conducted extensive analyses in all three areas in order to correctly identify the optimum engine geometry that provides the best opportunity to have a highly efficient internal combustion engine. In-cylinder simulations have shown that the heat transfer increases rapidly below a stroke-to-bore ratio of about 2, engine systems simulations have shown that the pumping work increases rapidly below a stroke-to-bore ratio of about 2.
This fact allows an opposed-piston engine to have much larger stroke-to-bore ratios than an engine with one piston per cylinder without having excessively high mean piston speeds that are detrimental to inertial loading and friction.
- Pumping terms
- Stroke-to-Bore Ratio: A Key to Engine Efficiency
- Difference Between HP and BHP
For context, below is a plot of power density versus stroke-to-bore ratio of some current four-stroke engines designed for a wide range of applications.