BUET ENGINEERS

Mechanical engineering one liner A nozzle is said to be a convergent nozzle when the cross-section of the nozzle decreases continuously from entrance to exit. A turbine is said to have an axial discharge when the steam leaves the blade tip at 90° to the direction of the blade motion. The flow through a nozzle is regarded as isentropic flow. The ratio of total useful heat drop to the total isentropic heat drop, is called internal efficiency. The pressure at which the steam leaves the nozzle is known as back pressure. The discharge of steam in a convergent-divergent nozzle remains constant after the throat (i.e. in the divergent portion of the nozzle). The rate of discharge through the nozzle increases when the exit pressure is gradually reduced. In a nozzle, whole frictional loss is assumed to occur between throat and exit The impulse reaction turbine has its driving force partly as an impulsive force and partly as a reaction force. A regenerative steam cycle renders...

Mechanical engineering One liner Hooke's law holds good up to Limit of proportionality. Young's modulus is defined as the ratio of Longitudinal stress and longitudinal strain. The materials having same elastic properties in all directions arc called Isotropic materials. A thin mild steel wire is loaded by adding loads in equal increments till it breaks. The extensions noted with increasing loads will behave as under Increase uniformly first and then increase rapidly. Modulus of rigidity is defined as the ratio of Shear stress and shear strain. The ultimate tensile stress of mild steel compared to ultimate compressive stress is More. The impact strength of a material is an index of its Toughness. The Young's modulus of a wire is defined as the stress which will increase the length of wire compared to its original length with same amount. Percentage reduction of area in performing tensile test on cast iron may be of the order of zero. The intensity of stress...

  MECHANICAL ENGINEERING ONE LINER  1. What is the difference between scavenging and supercharging ? Scavenging is process of flushing out burnt gases from engine cylinder by introducing fresh air in the cylinder before exhaust stroke ends. Supercharging is the process of supplying higher mass of air by compressing the atmospheric air. 2. What are the names given to constant temperature, constant pressure, constant volume, constant internal energy, constant enthalpy, and constant entropy processes. Isothermal, isochroic, isobaric, free expression, throttling and adiabatic processes respectively. 3. In a Rankine cycle if maximum steam pressure is increased keeping steam temperature and condenser pressure same, what will happen to dryness fraction of steam after expansion ? It will decrease. 4. Why entropy change for a reversible adiabatic process is zero ? Because there is no heat transfer in this process. 5. What are two essential conditions of perfe...

MECHANICAL ENGINEERING ONE LINER 1. What is the difference between isotropic and anisotropic materials? If a material exhibits same mechanical properties regardless of loading direction, it is isotropic, e.g., homogeneous cast materials. Materials lacking this property are anisotropic. 2. What are orthotropic materials?  It is a special class of anisotropic materials which can be described by giving their properties in three perpendicular directions e.g. wood; composites. 3. What is view factor?  View factor is dependent upon geometry of the two surfaces exchanging radiation. 4. What properties need to be considered for applications calling for following requirements:  (i) Rigidity (ii) Strength for no plastic deformation under static load. (iii) Strength to withstand overload without fracture. (iv) Wear resistance  (v) Reliability and Safety.  (i) Rigidity—Elastic modulus and yield strength...