Name: adiabatic compression in an engine cylinder
Uploaded: 2025-05-22T09:05:49.000Z
Duration: 1 min 20 s
Channel: JoVE

K12 Standards

Florida Department of Education

High School

Physical Science

SC.912.P.10

SC.912.P.10.2

Work Done in an Adiabatic Process

ヘリウムガスを充填した気象観測気球で、初期圧力と体積が上昇し、大気圧が下がると最終体積まで無断熱に膨張するとします。ガスによって行われる仕事は何ですか?
初期温度と最終温度がわかっている場合、断熱プロセスの場合、行われる仕事は、温度変化で表されるその内部エネルギーから得られます。
別の方法は、断熱プロセスの条件を使用することであり、そこからガスの初期圧力と最終圧力、および体積を関連付けることができます。用語は、簡略化するために再配置されています。
体積変化中の作業を思い出し、得られた圧力表現をその中に置き換えます。
この式を体積変化と統合することにより、断熱プロセス中に行われた作業を決定できます。
ヘリウムバルーンの初期ガス圧力が1気圧で、バルーンの体積が25 m3から100 m3に変化する場合、導出された式に既知の量を代入することにより、ガスによって行われた仕事を計算することができます。

<ol>
	<li>ヤング、H.D.およびフリードマン、RA(2012)。現代物理学と大学物理学。カリフォルニア州サンフランシスコ:ピアソン。641、642ページ</li>
	<li>OpenStaxです。(2019). 大学物理学 Vol.2.【Web版】。<a href="https://openstax.org/books/university-physics-volume-2/pages/3-6-adiabatic-processes-for-an-ideal-gas" から取得>https://openstax.org/books/university-physics-volume-2/pages/3-6-adiabatic-processes-for-an-ideal-gas</a></li>
</ol>

断熱プロセスで行われる作業

自動車のディーゼル エンジンのシリンダー内の理想気体の断熱圧縮を考えてみましょう。 ガソリン蒸気は、ピストンが膨張位置にあるときに自動車エンジンのシリンダー内に噴射されます。 得られたガスと空気の混合物の温度、圧力、体積は 20℃、1.00 x 105 N/m2、240 cm です。 >3 、それぞれ。 次に、混合物を断熱的に圧縮して体積を 40 cm3 にします。 ここではそのように仮定していますが、自動車エンジンの実際の動作では、圧縮は準静的ではないことに注意してください。 圧縮後の混合物の圧力と温度は何度ですか? 圧縮中に行われる作業は何ですか?

解決策:

断熱圧縮プロセスの場合、圧力の式は次のように記述されます。

<img alt="Equation1" src="/files/ftp_upload/13689/13689_Equation_1.svg" style="text-align: center; height: 34px;" />

空気のモル熱容量比を 1.4 として、既知の量を式 (1) に代入することで、圧縮後の混合物の圧力が計算されます。

<img alt="Equation2" src="/files/ftp_upload/13689/13689_Equation_2.svg" style="text-align: center; height: 34px;" />

理想気体の法則と得られた圧力値を使用して、圧縮後の混合物の温度も計算されます。

<img alt="Equation3" src="/files/ftp_upload/13689/13689_Equation_3.svg" style="text-align: center; height: 34px;" />

<img alt="Equation4" src="/files/ftp_upload/13689/13689_Equation_4.svg" style="text-align: center; height: 34px;" />

<img alt="Equation5" src="/files/ftp_upload/13689/13689_Equation_5.svg" style="text-align: center; height: 10px;" />

このようにして、自動車のディーゼル エンジンのシリンダー内の圧縮後の混合気の圧力と温度が決定されます。

圧縮プロセスが等温である場合、圧力の値は取得された値から変化します。 断熱圧縮過程では温度が上昇すると圧力が大きくなるからです。 したがって、圧縮行程付近でシリンダーに燃料を噴射すると、混合気がより高温になり、点火プラグを必要とせずに燃料が自然点火します。

初期圧力と最終圧力を知ることで、圧縮中に行われた仕事を次のように取得できます。

<img alt="Equation6" src="/files/ftp_upload/13689/13689_Equation_6.svg" style="text-align: center; height: 34px;" />

既知の量と取得した量を上の式に代入すると、行われる仕事は -1.63 J に等しくなります。ここで、マイナス記号は、仕事が空気とガスの混合物に対してピストンによって行われることを示します。

自動車のディーゼルエンジンのシリンダー内の理想気体の断熱圧縮を考えてみましょう。ガソリン蒸気は、...

Education

JoVE Core

Physics

物理学

Unit 1

ユニット1

The First Law of Thermodynamics

熱力学第一法則

KEY TERMS AND CONCEPTS

主要用語と概念

adiabatic compression in an engine cylinder

Adiabatic compression in an engine cylinder changes the pressure, temperature, and volume of a gas-air mixture. In this setup, gasoline vapor is injected into the cylinder when the piston is in its expanded position. The mixture starts at 20 °C, 1.00 x 10^5 N/m^2, and 240 cm^3.

The mixture is then compressed adiabatically to 40 cm^3. Adiabatic means no heat is exchanged with the surroundings during the process. For this calculation, the compression is treated as quasi-static, even though real automobile engine compression is not quasi-static.

Using the adiabatic pressure relation and the molar heat capacity ratio for air, 1.4, the final pressure is found from the initial conditions and the volume change. The ideal gas law is then used with that pressure to calculate the final temperature of the mixture. The result shows that the compressed gas reaches a higher pressure and temperature than it had before.

If the compression were isothermal, the pressure would be different from the value found here. In an adiabatic compression, the temperature rises, so the pressure becomes greater. This helps explain why fuel injected near the compression stroke can ignite on its own in a diesel engine, without spark plugs.

The work done during compression is found from the initial and final pressure values. The calculated work is -1.63 J. The negative sign means the piston does work on the air-gas mixture during compression.

Adiabatic Compression in an Engine Cylinder

adiabatic-compression-in-an-engine-cylinder

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Adiabatic compression in an engine cylinder changes the pressure, temperature, and volume of a gas-air mixture. In this setup, gasoline vapor is injected into the cylinder when the piston is in its expanded position. The mixture starts at 20 °C, 1.00 x 10^5 N/m^2, and 240 cm^3. The mixture is then compressed adiabatically to 40 cm^3. Adiabatic means no heat is exchanged with the surroundings during the process. For this calculation, the compression is treated as quasi-static, even though real...

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Adiabatic Compression in an Engine Cylinder | JoVE K12

physics

JoVE Core 物理学は、運動学、力学、流体力学、静力学、波動、音響などの基礎的な物理学の理論と応用を、簡潔でわかりやすいアニメーション ビデオで紹介します。さらに、科学者の実際のビデオでは、世界中の今日の研究所で行われている古典的および独自の研究実験における関連概念の適用を示しています。

SC.912.P.10.3

new-york-state-science-learning-standards

New York State Science Learning Standards

HS. Energy

HS-PS3-3.

Energy Basics

Chemical reactions, such as those that occur when you light a match, involve changes in energy as well as matter.

Chemical changes and their accompanying ...

First Law of Thermodynamics

Energy Conservation

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Internal Energy

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Energy

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Types of Potential Energy

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Types of Kinetic Energy

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Kinetic Energy - I

It&#8217;s plausible to suppose that the greater the velocity of a body, the greater effect it could have on other bodies. This does not depend on the ...

Kinetic Energy - II

The kinetic energy of a particle is one-half of the product of the particle&#8217;s mass and the square of its speed. Note that just as Newton&#8217;s ...

Work-energy Theorem

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Work and Energy for Variable Forces

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Work-Energy Theorem for Motion Along a Curve

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Conservation of Energy: Application

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Differentiate among the various forms of energy and recognize that they can be transformed from one form to others.

SC.912.P.10.1

Thermodynamic Systems

A thermodynamic system is a set of objects whose thermodynamic properties are of interest. The system is considered to be embedded in its surroundings or ...

Work Done During Volume Change

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Path Between Thermodynamics States

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Heat and Free Expansion

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The internal energy of a thermodynamic system is the sum of the kinetic and potential energies of all the molecules or entities in the system. The kinetic ...

A change in the internal energy of a system depends on the the net heat transfer into the system and the net work done by the system. The first law of ...

First Law Of Thermodynamics: Problem-Solving

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Cyclic Processes And Isolated Systems

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In the case of a ...

Isothermal Processes

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Isochoric and Isobaric Processes

A thermodynamic process that occurs at constant volume is called an isochoric process. According to the first law of thermodynamics, heat supplied or ...

Consider the adiabatic compression of an ideal gas in the cylinder of an automobile diesel engine. The gasoline vapor is injected into the cylinder of an ...

Thermodynamic Potentials

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Maxwell's Thermodynamic Relations

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Joule-Thomson Effect

The Joule-Thomson effect, also known as the Joule-Kelvin effect, describes the temperature change of a fluid when it is forced through a valve or porous ...

Explore the Law of Conservation of Energy by differentiating among open, closed, and isolated systems and explain that the total energy in an isolated system is a conserved quantity.

Energy and Work

Source: Ketron Mitchell-Wynne, PhD,&#160;Asantha Cooray, PhD, Department of Physics &#38; Astronomy, School of Physical Sciences, University of ...

Enthalpy

Entropy

Power

The concept of work involves force and displacement; meanwhile, the work-energy theorem relates the net work done on a body to the difference in its ...

Power Expended by a Constant Force

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Compare and contrast work and power qualitatively and quantitatively.

Mechanisms of Heat Transfer I

Just as interesting as the effects of heat transfer on a system are the methods by which the heat transfer occur. Whenever there is a temperature ...

Mechanisms of Heat Transfer II

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Absorption of Radiation

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Describe heat as the energy transferred by convection, conduction, and radiation, and explain the connection of heat to change in temperature or states of matter.

SC.912.P.10.4

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Relate temperature to the average molecular kinetic energy.

SC.912.P.10.5

Chemical Reactions

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Dynamics of Circular Motion

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Dynamics Of Circular Motion: Applications

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The principle of superposition applies to gravitational forces of objects that are sufficiently far apart. It states that the net gravitational force on a ...

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Create and interpret potential energy diagrams, for example: chemical reactions, orbits around a central body, motion of a pendulum.

SC.912.P.10.6

A. Energy is involved in all physical and chemical processes. It is conserved, and can be transformed from one form to another and into work. At the atomic and nuclear levels energy is not continuous but exists in discrete amounts. Energy and mass are related through Einstein's equation E=mc2.

B. The properties of atomic nuclei are responsible for energy-related phenomena such as radioactivity, fission and fusion.

C. Changes in entropy and energy that accompany chemical reactions influence reaction paths. Chemical reactions result in the release or absorption of energy.

D. The theory of electromagnetism explains that electricity and magnetism are closely related. Electric charges are the source of electric fields. Moving charges generate magnetic fields.

E. Waves are the propagation of a disturbance. They transport energy and momentum but do not transport matter.

Adiabatic Compression in an Engine Cylinder

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